The present invention relates to liquid phase process for oxidizing an ester of a para- or meta-methyl-substituted phenol selected from the group consisting of p-cresol, m-cresol, 3,4-dimethylphenol, 3,5-dimethylphenol and 3,4,5-trimethylphenol to produce an aromatic carboxylic or polycarboxylic acid. These acids are useful in liquid crystal polymers and polymers useful in engineering plastics. More particularly, the invention relates to a liquid phase process for the production of p-acetoxybenzoic acid and acetate esters of other phenolic compounds in high yield.
p-Acetoxybenzoic acid, as the acetylated derivative of p-hydroxybenzoic acid, is an important monomer for production of liquid crystal polymers. The acetylation step is normally quantitative, after p-hydroxybenzoic acid has been purified, usually by crystallization to remove by-products formed in the preparation of the p-hydroxybenzoic acid. 4-Acetoxylphthalic anhydride, the acetoxylated derivative of 3,4-dimethylphenol, is useful in production of ester-imide polymers for engineering applications.